1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming apparatus, and more particularly to a sheet processing apparatus for performing a cutting process to a booklet formed by stapling a plurality of sheets and conveying it and an image forming apparatus including the sheet processing apparatus.
2. Description of the Related Art
Conventionally, a sheet processing apparatus having a cutting apparatus for improving the appearance of a sheet bundle as a product by folding the central portion of sheets and cutting an edge of the sheet bundle folded to two portions at a stapled position thereof is widely known in Japanese Patent Application Laid-Open No. 2000-198613 and the like.
As shown in, for example, FIG. 12, the sheet processing apparatus conveys once a saddle-stapled booklet S between upper and lower cutting blades 51, 52 and cuts the booklet S located therebetween by lowering the upper blade 51 to the lower blade 52. Cutting wastes generated as cut pieces by cutting the sheets drop by self weight and are accommodated in a dust box 53 located therebelow.
In FIG. 12, a swing guide 54 guides the sheet bundle from a conveying belt 55 to the lower blade 52 when the bundle passes as well as swings and moves down when the sheets are cut and evacuates so that it does not prevent the cutting waste from dropping into the dust box 53. On the completion of cutting, the swing guide 54 swings and moves upward again and guides a next a bundle. Thereafter, the cut booklet S is conveyed to a not shown bundle accommodation unit and accommodated therein again.
However, in the conventional apparatus since the cut wastes drop into the dust box by the self weight, when they are subjected to external resistance (static electricity, air resistance, sliding resistance), they may not drop into the dust box 53. When the wastes cannot drop within a predetermined time, the swing guide 54, which is moving downward, moves upward again and closes a path to the dust box. Thus, even if the cutting wastes can drop, they remain on the swing guide 54. This phenomenon is liable to occur when cutting wastes has a small self weight, that is, their width is set to a small size.
Further, when the cutting wastes moves in a conveying path, sensors in the conveying path ordinarily cannot identify sheets and erroneously detect them, from which failures occur in control. Exemplified as the failures, are, for example, a failure of adding the number of cutting wastes to the number of counted sheets, a failure of erroneously recognizing that an interval between sheets is narrowed by detecting cutting wastes and feeding back the recognition to an inter-sheet control at the side providing sheets.